Friction material

Abstract

This disclosure is directed to a friction material which includes a porous material and capsules containing a hydrophobic substance in a liquid form. The porous material and capsules are formed into a composite structure by a binding agent so as to use the hydrophobic substance contained in the capsules for a component of a lubricating layer to be formed on the friction material upon breakage of the capsules.

What is claimed is: 
     
       1. A friction material for a clutch or brake which comprises a soft porous material and capsules containing therein a lubrication material comprising a hydrophobic substance in a liquid form, said porous material and said capsules being formed into a composite structure by a binding agent, said lubrication material forming a lubrication layer on said friction material upon breakage of said capsules said lubrication material being present in said capsules in an amount sufficient to provide uniform lubrication upon breakage of said capsules and yet good adhesion of said friction material to a substrate. 
     
     
       2. A friction material as claimed in claim 1, wherein shells of said capsules are made of a thermoplastic resin which can be re-softened by heat. 
     
     
       3. A friction material as claimed in claim 2, wherein said thermoplastic resin is of methyl methacrylate acrylonitrile copolymer having a softening temperature of approximately 100° C. 
     
     
       4. A friction material as claimed in claim 1, wherein said binding agent is of phenol resin. 
     
     
       5. A friction material as claimed in claim 1, wherein said hydrophobic substance in the liquid form which is the content of said capsules is present at least more than 18% by weight in said friction material. 
     
     
       6. A friction material as claimed in claim 1, wherein said porous material is of cork particles. 
     
     
       7. A friction material as claimed in claim 1, wherein said hydrophobic substance is of alpha-olefin having a dynamic viscosity of 28 cst at 40° C. 
     
     
       8. A process of manufacturing a friction material which comprises the steps of mixing 100 parts by weight of cork particles, 80 parts by weight of phenol resin (50 wt% of non-volatile component), and 60 parts by weight of capsules each containing hydrophobic substance in a liquid form, subjecting the mixture thus prepared to heating and compression in a metallic mold at temperatures of 130° C.±10 degrees for 90 minutes, and taking out the mixture thus heated and compressed in the metallic mold out of said metallic mold for subsequent shaping into the friction material in which said capsules are broken. 
     
     
       9. A process of manufacturing a friction material which comprises the steps of mixing 100 parts by weight of cork particles, 80 parts by weight of phenol resin (50 wt% of non-volatile component) having a low polymerizing temperature, and 60 parts by weight of capsules each containing hydrophobic substance in a liquid form, subjecting the mixture thus prepared to heating and compression in a metallic mold at temperatures of 60° C.±10 degrees for 90 minutes, and taking out the mixture thus heated and compressed in the metallic mold out of said metallic mold for subsequent shaping into the friction material in which said capsules are not broken.